1. Field of the Invention
The present invention relates to a rainfall determination apparatus and to a method suitable for an automatic lighting system for vehicles, or the like.
Priority is claimed on Japanese Patent Application No. 2004-103519, filed Mar. 31, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In a known rainfall determination apparatus and method applied to vehicles, clocking and counting of the number of times of wiping are performed in accordance with each operation mode of the wiper (i.e., intermittent, low speed, or high speed mode), and rainfall is detected (i.e., it is determined that there is rain) when the clocked time and the counted number of times of wiping respectively reach specific values (see Japanese Unexamined Patent Application, First Publication No. 2000-168435, etc.). More specifically, in the intermittent mode, a timer for clocking a first time and a counter for counting the number of times of wiping within the first time are provided, and in each of the low speed mode and the high speed mode, a timer and a counter corresponding to the mode are also provided, which are controlled by specific conditions corresponding to each operation mode of the wiper.
However, such timer and counter for exclusive use for each operation mode of the wiper, which are controlled by conditions depending on each mode, make the structure of the rainfall determination apparatus and method complicated. In particular, in consideration of application of the rainfall determination apparatus and method to an automatic lighting system for vehicles, the automatic lighting system itself is a relatively expensive system due to usage of an illumination sensor and the like, and the above complication in the structure causes further increase in the system's expense. Accordingly, vehicles to which the system can be applied are limited, thereby reducing flexibility.